Multi-point sampling and measurement system for exhaust smoke from inlet and outlet of denitration CEMS of thermal power plant

Abstract

The invention discloses a multi-point sampling and measurement system for exhaust smoke from an inlet and an outlet of a denitration CEMS of a thermal power plant. The multi-point sampling and measurement system comprises a back flushing device and two exhaust smoke analyzers, and further comprises an exhaust smoke gathering tank and more than 2 inlet sampling devices; a detection probe of each inlet sampling device extends into a sampling opening on a flue inlet, and the output end of each detection probe is connected with a sampling pipe; each sampling pipe is communicated with the inlet of the exhaust smoke gathering tank through each inlet sampling device; the outlet of the exhaust smoke gathering tank is connected with the inlet exhaust smoke analyzer through a pipeline; the back flushing device is communicated with the sampling pipes through compressed air pipes. According to the multi-point sampling and measurement system, the original design with only one sampling device is improved into the design with multiple sampling devices, so that NOx exhaust smoke with different concentrations can be obtained and then is conveyed to the exhaust smoke analyzers for measurement after being mixed. Therefore, a measurement value is more accurate and stabler, and the probability of over-spraying and under-spraying of ammonia is greatly reduced; a purging device is used for regularly and automatically purging the sampling pipes, so that the possibility that the sampling pipes are blocked is effectively reduced.

Description

technical field [0001] The invention relates to a flue gas monitoring system in the denitrification technology of a thermal power plant, in particular to a multi-point sampling and measurement system for flue gas at the entrance and exit of a denitrification CEMS in a thermal power plant. Background technique [0002] In the denitrification process of flue gas in thermal power plants, the accuracy of the flue gas analysis instrument at the denitrification inlet and outlet to measure NOx is related to the denitrification efficiency, the automatic adjustment of denitrification, and whether the NOx in the denitrification outlet meets the environmental protection emission standards. Therefore, the NOx at the denitrification inlet and outlet Real-time accurate measurement plays a key role. [0003] The desulfurization process of the current thermal power plant is generally carried out in the once-through boiler, and the selective catalytic reduction reaction is adopted. The react...

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Problems solved by technology

[0004] 1) Since the denitrification reactor adopts the traditional high-dust arrangement, there is only one sampling port at the inlet and outlet of each reactor, and it is very easy to cause blockage of the sampling tube in the case of heating tape and backflushing

Once the sampling pipe is blocked by dust, it will not only affect the measurement of the flue gas, but also cause the automatic ammonia injection to jump out of the automatic, resulting in the NOx content of the flue gas exceeding the standard;

[0005] 2) The uniformity of ammonia injection in the denitrification reactor and the uncertainty of the reaction lead to uneven distribution of NOx at the outlet of the reactor, and the concentration of NOx obtained by sampling at different sampling points is different, or the concentration varies greatly

If only one sampling point is used to represent the NOx concentration distribution in the entire flue, there will be a large deviation. When the deviation reaches a certain level, there will be over-injection and under-injection of ammonia. Under-injection of ammonia is due to incomplete reaction. , will lead to excessive NOx at the outlet; and over-spraying ammonia will lead to an increase in the amount of ammonia escape, and excessive ammonia escape will affect downstream equipment, which is not conducive to the safe operation of the unit

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